The objective is to understand the dynamic biochemistry of synaptic junctions, a region that must support both conduction and trophic relationships between neurons. We propose to continue our quantitative investigations on specific proteins that are involved in the functions of synapses by studies of the membranes of cholinergic synapses and their integral and attached structure and macromolecules, in both their static composition and their dynamic properties with regard to modification and turnover. This is to be accomplished by 1) continued exploration, exploitation and extension of our current studies on the proteins present in and on synapses. The aims here are a) to separate and investigate the nature and b) the localization of the glycoproteins present on or in the surface membranes of synaptosomes, including c) their mode of biosynthesis; as well as to d) determine the turnover i) of the acetylcholinesterase associated with synaptosomal membranes, ii) of the nicotinic (alpha-bungarotoxin binding) acetylcholine receptors, iii) of dopamine-beta-hydroxylase and iv) of neurofilaments. 2) Adaptation of old and development of new techniques for the identification, isolation and characterization of component membranes of synaptosomes and their synaptic junctional complexes. The aims here are to a) isolate junctional complexes containing and specific for the nicotinic receptor, b) resolve them into their pre- and post-synaptic portions and c) investigate the surface topography and functional organization of each, with special emphasis on the localization and potential function of the fibrous proteins tubulin, actin and filarin. 3) A determination of the potential capabilities of the entities under 2) for change and modification. The aims here are to investigate a) the differential effects of controlled proteolysis and b) their response to repeated chemical stimulation in vitro. BIBLIOGRAPHIC REFERENCES: Y-J. Wang and H. R. Mahler. Topography of the Synaptosomal Plasma Membrane. J. Cell Biol., in press (1976). P. M. Salvaterra and H. R. Mahler. Nicotinic Acetylcholine Receptor from Rat Brain: Solubilization, Partial Purification and Characterization. J. Biol. Chem., in press (1976).